The invention relates to a converter circuit, having three inputs to each one of which a bivalent color signal R, G or B is supplyable, for converting these bivalent color signals into a monochromatic signal (Y) obtainable at an output thereof with an amplitude which is different for each color combination, the converter circuit comprising an adder circuit.
Wireless World no. 1486, June 1976 page 53 and no 1480 December 1975 page 565, discloses a converter circuit of the above-defined type for obtaining a monochromatic signal from a color signal combination obtained from a Teletext or Viewdata signal. The grey scale obtained with this circuit is poor and is unsatisfactory for color signals corresponding to low brightnesses.